1. Field of the Invention
The present invention relates to an electrophotographic image forming apparatus and more particularly to a toner agitating device and a toner conveying device for use in a printer, facsimile apparatus, copier or similar electrophotographic image forming apparatus of the type using a single-component type developer.
2. Description of the Background Art
It is a common practice with an image forming apparatus of the type described to use a hard bottle as a toner container for storing dry toner or carrier or a mixture thereof (represented by toner hereinafter), which constitutes a developer. For example, a toner cartridge, which is a specific form of a hard bottle, may be provided with an agitator or toner agitating and discharging means therein. Alternatively, a spiral groove may be formed on the inner periphery of the toner cartridge, so that toner can be moved and discharged when the toner cartridge is rotated. Further, the toner cartridge may not be provided with any toner discharging mechanism, in which case toner is discharged by manual operation.
Today, in parallel with the trend toward the reduction of wastes for coping with environmental problems, there is an increasing demand for the collection and recycling of toner containers. While a soft, foldable container, which has been proposed in various forms in the past, is an implementation that meets the above demand, dry toner for electrophotography generally lacks fluidity and is apt to cohere and therefore cannot be easily discharged from a soft container. More specifically, it is difficult to arrange in a soft container rigid members for supporting mechanical parts that agitate and discharge the above toner, i.e., an agitator and a discharging mechanism. Further, the discharging mechanism obstructs the reduction of the volume of the soft container. Even if the soft container is operated by hand for discharging the toner, the soft container is not easy to handle.
In light of the above, there has been proposed a system that feeds air to the inside of a flexible container for thereby agitating and fluidizing toner stored in the container and sucks the toner out of the container with a powder pump, i.e., single-axis eccentric screw pump. Japanese Patent Laid-Open Publication No. 2000-351445, for example, proposes to use an air pump as means for feeding air to the inside of a soft container for the above purpose. As for agitation using air, however, it is necessary to give consideration to the amount of air to be fed that varies in accordance with the amount of toner remaining in the container; the former increases with an increase in the latter or decreases with a decrease in the latter.
It has been customary to feed air at a constant flow rate with a single air pump without regard to the amount of toner remaining in a soft container. This brings about a problem that when the amount of toner remaining in a soft container is great, the amount of air is apt to be short and fail to sufficiently agitate the toner, resulting in defective toner replenishment, i.e., causing much toner to remain in the container. On the other hand, when the amount of toner remaining in the container is small, it is likely that the bulk density of the toner and therefore the amount of replenishment decreases, lowering image density.
Japanese Patent Laid-Open Publication Nos. 11-282236 and 2000-351445, for example, each disclose a powder conveying device of the type replenishing toner from a bag-like or soft toner container by with a suction type powder pump. Further, Japanese Patent Laid-Open Publication Nos. 2000-137376 and2000-227706, for example, each propose to combine an air pump and a powder pump generally referred to as a Mono pump. However, such prior art schemes all feed air without regard to the amount of toner remaining in a toner container.
While Japanese Published Patent No. 10-500610, for example, teaches a liquid discharging container with a refilling container relating to a mechanism for opening and closing the cap of a toner container, it is not a solution to the problems stated above.